Calculate your estimated due date, conception date, gestational age, and key pregnancy milestones from your last menstrual period (LMP) or conception date.
Calculate your estimated due date (EDD), current gestational week, trimester, and key pregnancy milestones. Supports three calculation methods: Last Menstrual Period (LMP), conception date, or IVF embryo transfer date. Based on Naegele's rule.
The most common method uses your Last Menstrual Period (LMP): add 280 days (40 weeks) to the first day of your last period. This is Naegele's rule, developed in the 1800s and still the standard today. It assumes a 28-day cycle with ovulation on day 14.
If you know your conception date, the EDD is 266 days (38 weeks) later. For IVF, the calculation uses the embryo transfer date: add 266 days minus the embryo age (5 days for a blastocyst transfer, 3 days for a day-3 transfer).
Only about 4% of babies are born on their exact due date. Most are born within 2 weeks before or after. Due dates are best understood as the center of a 5-week window (weeks 38–42). Your healthcare provider may revise your due date based on an early ultrasound, which is more accurate than LMP calculations — especially if your cycles are irregular.
Conception date is more precise if you know it, but LMP (Last Menstrual Period) is the clinical standard because conception date is often uncertain. An early ultrasound is the most accurate method.
Gestational age counts from your LMP — typically 2 weeks before conception. Fetal age counts from conception. Doctors use gestational age, so a "10-week pregnancy" means roughly 8 weeks since conception.
How Pregnancy Due Dates Are Calculated